The present invention relates to a sheet- or web-shaped packaging blank including longitudinal material weakenings along which the packaging blank is intended to be folded on forming into packages.
Within packaging technology, use is often made of packages of single-use disposable type, and a very large group of these so-called single use disposable packages is produced from a laminated, sheet- or web-shaped packaging blank comprising a relatively thick fibre layer of paper or paperboard and outer, liquid-tight coatings of plastic. In certain cases, in particular in conjunction with especially perishable and oxygen gas sensitive products, the packaging blank also displays an aluminum foil (Alifoil) in order to impart to the packages superior gas and light barrier properties.
Prior art single use packages are most generally produced with the aid of modern packing and filling machines of the type which both forms, fills and seals finished packages from a sheet-or web-shaped packaging blank. From, for example a web-shaped packaging blank, the packing and filling machine produces packages in that the web is first formed into a tube. The tube is filled with the pertinent contents and is divided into closed, filled package units. The package units are separated from one another and given the desired geometric configuration, normally parallelepiped, by a forming operation prior to discharge from the packing and filling machine for further transport and handling of the finished packages.
In order to facilitate the forming of the packaging blanks into packages, the packaging blank is, right from the outset, provided in a per se known manner with a suitable pattern of linear (both longitudinal and transverse) material weakenings or crease lines along which the packaging blank is intended to be folded on its forming into packages. In addition to facilitating fold-formation of the packaging blank, the linear material weakenings also contribute in imparting to the finished packages mechanical strength and stability so that the packages may be stacked and handled without the risk of being deformed or otherwise destroyed under normal handling. With the aid of the fold-facilitating material weakenings, the production is moreover made possible of packages of optional specially configured appearance which the packages maintain throughout their entire service life.
In a prior art method, a packaging material of paper or paperboard is provided with a desired pattern of linear material weakenings by mechanical processing of a web of the packaging material by means of a rotary roller which, on its peripheral surface, displays a corresponding pattern of linear radial projections. In this instance, the web is led through the nip between the rotating roller and a substantially smooth, but elastically yieldable counterpressure roller, the radial projections being urged against the one planar side of the web for compaction and xe2x80x9ccrushingxe2x80x9d of the fibres within the regions of the engagement of the radial projections with the web. The web provided with crease lines is thereafter provided with at least one additional layer of plastic and/or other material by a lamination operation in order to impart to the packaging material the desired tightness and sealing properties prior to the forming of the packaging material into packages.
While a packaging material with fold-facilitating material weakenings within which the fibres are compacted and wholly or partly crushed does make for a simple fold-formation of the material, it has nevertheless proved difficult to produce attractive and stackable packages with the sought-for straight and well-defined folding edges and desired mechanical grip rigidity. Problems inherent in not entirely straight folding edges are particularly serious in large packages where straight folding edges are required in order to be able reliably to stack packages on one another without an excessive risk that the vertical fold edges of subjacent packages taking up the load in the stack are buckled or deformed during transport and normal handling of stacked packages.
One object of the present invention is therefore to obviate the above-discussed drawbacks and disadvantages inherent in the prior art technology.
A further object of the present invention is to realise a packaging material of the type described by way of introduction with fold-facilitating material weakenings which make for a simple fold-formation of the packaging material into packages with the sought-for straight and well-defined folding edges.
Yet a further object of the present invention is to realise a packaging material provided with fold-facilitating material weakenings for packages with attractive and well-defined geometric outer configuration and appearance as well as superior mechanical stability and grip rigidity.
Still a further object of the present invention is to realise a packaging material provided with fold-facilitating material weakenings for mechanically stable and stackable packages in order to make for reliable handling of such packages stacked on one another.